This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The neuropeptide Substance P (SP) is involved in detection of noxious stimuli (nociception) by the nervous system. SP may diffuse several micrometres from neuronal release sites to target neurons which express the Neurokinin 1 receptor (NK1, "non-synaptic transmission"). How far neuropeptides can diffuse and how they interact within complex micro-environments surrounding their receptors remains unknown. This project will characterise the diffusion and receptor-binding kinetics of SP on NK1 receptor-expressing cell lines using Raster Image Correlation Spectroscopy (RICS). In addition, the interaction of the vasoconstrictor hormone Angiotensin II (AngII) and the AngiotensinII type 1 receptor (AT1) with SP and NK1 will also be investigated, to begin to understand how vasoactive hormones interact with neuropeptides to influence sympathetic neurons involved in regulating blood flow. Understanding the molecular mechanisms of non-synaptic transmission will enable more specific therapeutic interventions for conditions such as chronic pain. Understanding the interactions between vasoactive hormones and neuropeptides may provide valuable insights for the management of hypertension and hypertension-related disorders.